Propeller blade



July 8,1947. G. w. HARDY PROPELLER BLADE Filed June 16, 1943 INVOR.GORDON W f/neov Patented July 8, .1947

PROPELLER BLADE Gordon w. Hardy, Cleveland heights, Ohio, assignor toThe Marquette Metal Products Company, Cleveland, Ohio, a corporation ofOhio Application June 16, 194 3, Serlal No. 491,037

J 3 Claims.

This invention relates to a propeller blade particularly for aircraftand a new method of making such blade. I

One object of the invention is to provide a propeller blade which can bemade without any great amount of hand work and have strength,flexibility and other desirable characteristics comparable to, if notexcelling, the higher grades of laminated wooden propellers andall-metal propellers while at the same time being moisture and impactresistant and of light weight.

A further object is to provide an improved method of making metallicallyarmored propeller blades.

A specific object is to provide a propeller blade having an adequatelyreinforced core including high strength plastic material and an armorsheath partially or wholly covering the same of sumcient tensilestrength and impact resistance to prevent chipping and abrading of thepropeller surface as by projectiles, particularly at low temperatures. I

A further object is to provide a metallically armored propeller in whichthe armor is completely bonded to the core, whereby adequately to resistall tendency to peeling off, whether by impact or temperature efiects orotherwise.

Another object is to provide an improved propeller blade made partiallyfrom plastic material with an improved reinforcing core formedsubstantially as an integral part of a shank piece or butt of the bladesuitable for mounting in a metal hub provided with meansfor turning theblade about its longitudinal axis for pitch adjustment, feathering andthe like.

Another object is to provide a de-icing means for propeller blades whichmeans is operative efficiently to de-ice all the blade surfaces on whichice is likely to accumulate.

Further objects include the-provision of a propeller blade havingadequate tensile, compressive,

twist resisting and impact resisting strength, not-' withstandingrelatively light weight and resistance to the effects of temperaturechange and relative humidity or even immersion in water for longperiods.

Further objects and features of the invention will become apparent fromthe following description and by reference to the accompanying drawing,in which Fig. 1 is a front view of one blade of a propeller and a moreor less diagrammatic representation of a hub on which the blade may bemounted;

Fig. 2 is a sectional view showing, by way of example, a mold in whichpart of the core P013 tion of the blade can be formed, said viewshowing, in place in the mold, a metal shank or butt piece and innerreinforcing element rigid therewith;

Fig. 3 is a diagrammatic representation showing the manner of applyingarmoring metal to the completed core;

Fig. 4 is a relatively enlarged fragmentary cross sectional view showingparticularly the relationship of the de-icing fluid tube and dischargenozzle jets therefor at one edge portion of the blade;

Fig. 5 is a greatly enlarged (e. g. magnified) typical section of thecompleted blade near its surface; and

Fig. 6 is a view similar to Fig. 5 showing a modification in a plasticportion of the blade core or body.

Several prior proposals for the use of inorganic plastics as materialsfor propeller blades have been made, and it has also been proposed toprovide metal sheathing or armor for propeller blades made at leastpartially from plastics and for other non-metallic materials, as cores.Paper and fabric reinforced plastic cores of synthetic resin such asheretofore proposed require a great deal of labor to form them; andunder the extremely high bending and twisting strains to whichpropellers for aircraft are subjected as well as impact forces, thelaminations are apt to separate and the resinous material, beingbrittle,

is apt to fracture and become chipped or shattered. It has, in practice,usually been necessary to encase propellers made largely or wholly fromorganic plastics with a built-up partial or complete armor of metal ordope"-impregnated fabric in order to prevent contact of the plasticmaterials with moisture as well as in order to protect the plasticagainst being chipped or fractured by flying missles such as smallstones and,

in case of fighting craft, flak. The difference in twisting and bendingresistance or elasticity between the different materials heretofore usedand the differential of expansion and contraction under heat betweensaid different materials are common causes for short life on part ofcomposite propeller blades including such plastic materials asheretofore used or proposed.

In the present arrangement I have sought to reduce all the differentialswhich commonly account for deterioration and partial or completedestruction of composite blades by using a plastic material for the corewhich has great toughness, hardness comparable to metal, practically not den y to cold flow at moderately high temperatures or to fracture byimpact or strain at sub-zero temperatures and which has little, if any,tendency to separate locally from the metallic armor or other metalportionsduring subjection to rapid temperature changes and extremelyhigh bending and twisting strains. The unitary character of the blade ispreservedin part by a metallic armor of composite nature, one componentof which is selected for desirable bonding characteristics with theplastic as well as protection of the latter during application theretoand another component being selected principally with a view to greatersurface strength and abrasion resistance. The above are only the salientfeatures of the present method and propeller blade construction producedthereby. Others will be brought out later herein.

Referring further to the drawing. Fig. 1 shows a left hand portion of ablade in side elevation and a right hand portion in substantiallycentral principal plane section along the major surface of a reinforcingsheet and central core piece supporting the sheet. The blade has a shankor butt portion l suitably formed, for example, generally cylindrically.and with flange projections as at 2 which, in the form shown, arebuttress "thread effects for mounting the propeller in a suitable hub. Ahub is diagrammatically indicated at 3 with a tubular extension 4adapted to receive the pojections 2 and which may include provision forturning the entire blade about its longitudinal axis into high and lowpitch, feathering and/or reverse positions. Reference is directed to mycopending application, Serial No. 498,492 filed July 13, 1943, for asuitable hub construction providing for variable pitch as to the bladesof which there may be any suitable number and arrangement and for onemanner of supplying de-icing fluid to the blades. The ribs 2-on the buttportion I are, in actual practice, supported in split mounting sleevemembers such as shown for example in my copending application Serial No.476,398, filed February 19, 1943. For simplicity, the butt portion 1, asherein shown, is embraced by metal of the associated structure abovedescribed is secured between two hub extension 4 as though tunable forpitch adas at I in which event the reinforce will have cross passages asat 8 to enable injection of the plastic through the central bore andflow thereof outwardly-into a mold through such passages B inappropriate directions.

In addition to the reinforce 5, I preferably employ also a plate-likereinforce and plasticinterlocking element such as shown at Ill. Theelement I0 'is preferably in the form of a sheet metal blank 01 thegeneral shape of the main face portions of the blade but somewhatsmaller and having a fairly large number of passages ll therethrough.The passages are shown as comprising alternately oppositely necked orflanged openings through which the\plastic material at one side of thesheet In is adequately integrally bonded at intervals with the plasticon the other side of the sheet. The flanges present greater interlock orshoulder surfaces to the plastic than would plain punched-openings. Thesheet ill may be anchored to the reinforce 5 and/or to the butt piece 2,a convenient manner of fastening the sheet comprising slotting thereinforce bar 5 longitudinally as at i2, slipping the sheet into theslot and then brazing'or welding the sheet to the reinforce at thelateral limits of the slot. The sheet material is cut away centrally ofthe reinforce bar as at l3 so as not to obstruct the inlet duct 1 forthe plastic.

Assuming the composite shank and reinforcing appropriately heated moldmembers or dies-such as l5 and I6 which are separable substantiallyalong a plane parallel to the principal plane of the blade when formed,the plastic may be injected into the main mold cavity H as through anozzle I8 brought into sealing contact with an end wall of the buttpiece I at the central hole I of the butt piece. Suitable mold heatingand cooling means may include conduit passages formed in the mold as at20 for receiving alternately steam and water or other heating andcooling media; and such passages are appropriately spaced, proportionedand positioned so that the heat is properly distributed as required tocause the plastic entirely to fill the cavity ll under pressure beforeany partial solidification takes place.

Appropriate vents may be provided for discharging excess plastic as atthe tip-forming portion of the mold. The solidified plastic is indicatedin Figs. 1, 4 and 5 at 22.

The method outlined above for incorporating the plastic with the centralreinforce and butt piece structure is especially suited to the-plasticof a portion of the reinforce bar 5 are faced off as at 5a, as broughtout by comparison of Figs. 1, 2 and 4.

In order to form a firm and permanent intermaterials cellulose acetateand cellulose acetate butyrate which are preferred largely because oftheir high tensile and flexural strength, impact resistance, hardness,lack of brittleness and small tendency to elongate or cold flow" undermoderately high temperatures and to fracture under low temperatures. Theabove, of course, are only a few of the well known desirablecharacteristics I of the thermoplastic materials mentioned. Other 1plastics having similar properties may be considalong, or the reinforcebar hay have any other surrounds the reinforce 5 and determines theshape of the blade is to be formed by injection ered'operativeequivalents and within the scope of this patent. Thermosetting materialscan, of

' course, beusedand the molding methods would vary asbest fits theparticular plastic selected, whether thermosetting or thermoplastic,

molding as against transfer," "compression" or other molding methods anyof which could be practiced instead, then the butt pieceand re- 1 Apropeller blade form when ejected from the mold, such as shown in Fig.2, is then encased preferably in a complete envelope of metal. In

order to avoid joints in covering a preformed blade body made of wood orthe like with metal,

it has been proposed to treat such body with electrica-lly conductivesubstance sand'ithenv ap lyiithe metalgelectrolyticallyz'-':El'ec,trolytically zideposited metalr'ha's veryslittle tensilestrength-:ar'idds. moreover, squite I.brittle;s;:but-1 athe..principal-:disadvantage of its,.useaspropellerabladei ar'momorsheathinsxis that-it is:practically:impossiblejltoi secure ing-issuggestedgin Eig.-3 .-:wherein the spray noz-- zle forthemetal-,is'indicatediat 25 and the completed m'oldingflat 26:1? Themolding is mainly supported as by.th el shanlripiece 2 for rotation asby automatically variable speed gearingmechanismzsu'ggested,f-diagrammaticaily only, at 21. Additional supportis indicated at 28. Suitable means is also provided g-raduallyprogressively and automatically,to change the zone of operation of themetal spray in respect to the blade surface either by shifting the bladeor the nozzle continuously and "iria" direction parallel to thelongitudinal axis of the blade at the required speed; as, determined,bythe thickness of coating desired. Mechanisms for accomplishing suchmotions"; as referredtoabove are well known in themachine?tool-arts,,hence need no specific showingherelj; [-l

The. blade :jcore is spray coated locally, progressivelybyasuccessivesteps, .on both sides at nearly the same time during turning of theblade at appropriate'varying speeds as different surface portions"'areipresented to the nozzle. Thereby the tendency for the blade to be warped(as would be -the ,asei if one side were completely coated andthefi theother side) is greatly reduced and a more-. u'riiform andsmoother-coating can be obtained.

For the first coating which is applied directly onto the 'plastic andpreferably by the use of a fairly-low melting point metal such asaluminum, the-nozzle is positioned much farther away from thernoldingthan in the case of the second coating'since, in the first operation, itis desirable to prevent scorching or melting of the core by the hotmetal although sporadic softening of the plastic surfaces takes placeand slight penetration necessary for firmbonding of the first coating ofmetal therewith; and, in the second operation, detrimental effects ofheat are prevented by the insulative action of the underlying or firstmetal coating.

Incidentally, if the spray coating is done against the revolving andprogressively relatively advanced molding (e. g. moving the spray gunfor relative advancing) the application is in a more or less spiral pathabout the blade so that if there is any joint effect where one sprayingoperation overlaps metal deposited by the preceding operation, thejoint" will extend around the blade in a direction at right angles tothe longitudinal axis thereof rather than lengthwise of the blade at anypoint. Thus if the spraying operation starts at the tip the subsequentspray applications have a scale-like eflect, overlapping each othertoward the tip for greatest resistance to becoming detached bycentrifugal and abrasive forces during propeller operation.

The blade core is first given a complete and fairly light coating as ofaluminum or other low melting point metal (see Fig. 5 at 29). The lowermelting point metals have less tendency to scorch the plastic althoughsome of the particles embed themselves in the surface of the plastic andenhance the bonding. The first coat 29 forms a. protective layer uponwhich higher melting point metal, for example, steel, can be spraycoated as at 30 or possibly in some other manner, e. g. byelectroplating in case the low melting point metal of the first coat isadapted to be coated electrolytically. The bond 3| between the firstcoating 29 and the plastic 22 may be enhanced by having the surface ofthe plastic somewhat rough. Roughness or "tooth effect can be securedeither by a rough finish on the mold cavities or by sand blasting oretching of the plastic after molding (not illustrated.)

Another manner of enhancing the bond and, by the same means, reducingthe density hence total weight of the plastic component is suggested inFig. 6 wherein the plastic body 22a is shown as provided withinnumerable small cavities 34, formed as by introduction and dispersionof gasforming materials into the plastic stock, some of which cavitiesbreak through to the surface as at 35 and thereby form tooth effects formechanical bonding with the initial metal coating 29 in cases in whichthere is more thermal expansion differential than in the preferredselection of materials described above.

I have found that if the first coat is aluminum and the second coatsteel, the composite armor is adequate to serve all the functionsnormally served by sheet metal armor such as already known in thepropeller art, and it has the special advantages, namely full bondingover the entire coextensive surfaces; there are no joints, and the metalcan be increased in thickness as at the leading edge of the blade, assuggested by Fig. 4,

or at any such other portions as may be found to be subjected toespecially heavy duty.

Tube effects in propeller blades and cuffs for blades are already known,which tube effects are designed to distribute de-icing fluid to theblades during-rotation. So far as I know, however, it has not beenconsidered desirable to provide for distribution of such fluid frominside the blade proper to the outlying surface portions of the blades.The theory has been that a limited disthe leading edge which tubehasnozzle apertures, for example, of graduated size (reduced size out- Thede-icer fluid tube shown at 40 extends through an eccentric bore in thebutt piece I for connection as by flexible tubing 41 with a supply linewhich, for example only, is shown centrally of the hub 3diagrammatically at 42. The coupling and supply arrangement for thede-icer fluid tube from a pressure supply source is more completelyshown and is claimed inmy co-pending application Serial No. 498,492mentioned above.

The tube 40 leads from the butt piece I, to

2. A propeller blade comprising a central slotted metallic reinforcingbar tapering outwardly to a tip portion at one end, a perforated sheetmetal reinforcing element mounted in the slot in said bar, extendinglongitudinally. of said bar and laterally of the blade, a molded core oforganic plastic material surrounding said bar andv element and lockedthereto by interlocking. en-

gagement with the perforations of said element and with the slot insaidbar, and a protective metallic armor bonded .directly to said plasticcore. Y

' 3. A propeller blade comprising, a central slotted metallicreinforcing bar shaped at one end tov form a butt piece and taperingoutwardly at the other end to form a tip portion, a perforated sheetmetal reinforcing element mounted in the slot in said bar, extendinglongitudinally of said bar tributing alcohol or other de-icing fluidalong.

the camber surface portions 'of the blade. The actual effect ofdischarging such de-icing fluid from the blade as by suitable pressureapplied to the tube 40 is to volatilize the fluid in the zone ofoperation of the blades and the resulting mist of de-icer fluidaccomplishes the de-icing regardless of the particular region of theblade from which the fluid is discharged and onto what surface the fluidtends to flow. Unless, however, the- 1. A propeller blade comprising acentral hollow metallic reinforcing bar supported on a butt piece at oneend and tapered outwardly to a tip portion at the opposite end, aperforated sheet metal reinforcing element mounted on said bar,

extending beyond said tip portion and laterally of the blade, a moldedcore of organic plastic material surrounding said bar and element andlocked thereto by interlocking engagement with the perforations of saidelement and'withthe interior of said bar, and a protective metallicarmor bonded directly to said plastic core.

and laterally of the blade, a molded core of organic plastic materialsurrounding said bar and element and locked thereto by interlockingengagement withthe perforations of said element and with the slot insaid bar, and a protective metallic armor bonded directly tosaid plasticcore.

GORDON W. HARDY.

- REFERENCES CITED I The following references are of record in the fileof this patent: V

UNITED STATES PATENTS Number v v Name Date 1,419,180 Thomson etal. June13, 1922 11,843,886 Semmes Feb. 2, 1932 1,258,282 Welte .Mar. 5, 19182,063,019 Bardach et a1. Dec. 8, 1936 2,290,249 Piperoux July 21, 19422,217,979 Booharin Oct. 15, 1940 2,269,635 Mosehauer Jan. 13, 1942 1,384308 DeGiers July 12,1921 1,846,256 Havill Feb. 23, 1932 2,266,129Tegharty Dec. 16, 1941 1,308,527 Nilson July 1, 1919 1,860,655 BeebeAug. 2, 1932 2,077,959 Smith Apr. 20, 1937 1,385,802 St. John July 26,1921 FOREIGN PATENTS Number Country Date 674,727 Germany Apr. 21, 1939760,098 France Feb. 16,1934 341,540 .Italy June30, 1936 Great BritainJune 19, 1929

